Whereas recessive traits require two bad copies of a gene to become noticeable, a dominant trait expresses itself no matter what the other copy does. A benign example of dominance: If you inherit one gene for sticky wet earwax and one gene for dry earwax, the sticky earwax gene wins out every time.

No element gets people telling crazy stories like mercury does. People have told me tales about pharmacists waxing floors with mercury, mothers rubbing it into babies' skin to kill germs, and 10-year-olds coating dimes in it to make them shine, then blithely carrying them around in their pockets.

The density of space junk peaks around 620 miles up, in the middle of so-called low-Earth orbit. That's bad, because many weather, scientific, and reconnaissance satellites circle in various low-Earth orbits.

Sam Kean Quotes